Seal arrangement



Oct. 27, 1942- C. G. sul-rs 2,299,772

SEAL ARRANGEMENT Filed Oct. 17, 1941 Inventor'. Chauncey G. Suits,

by HM( ttorney.

Patented Oct. 27, 1942 SEAL ARRANGEMENT Chauncey G. Suits, Schenectady,N. Y., assg'nor to General Electric Company, a corporation of New YorkApplication October 17, 1941, Serial No. 415,484

8 Claims.

application relates to a seal adapted for use in electrical devices suchas transformers, capacitors and switches which contain a dielectricmedium at a pressure in excess of several atmospheres.

One of the objects is to provide an improved apparatus for supportingterminal structures and lead-in members.

Another object is to provide an improved means for reducing strain onthe terminal structures of apparatus employing diiierential pressures.

A further object is to provide a structure embodying cooperation betweeninsulated terminal members and the casing containing electricalapparatus in order to eliminate strain on the seal between theinsulation of the terminal members' and the casing.

While seals between insulating members and the casings of electricalapparatus are well known in the art, when high pressures are used insuch apparatus, diiiiculty has been encountered in satisfactorilyprotecting these seals. 'I'he diiierence between the pressure inthecasing and the outside atmosphere creates strains tending to break thebond with the seal either at the insulator or the casing. While the bondwith a casing may be protected by the use of welds and similar methodsof uniting metals, that with a vitreous or ceramic insulator is not soeasily protected.

My invention proposes to protect such a junction by providing additionalsupport at this point.

It is an important feature of the present invention to insulatingly sealan electrical conductor through a wall part having differentialpressures on opposite sides of the wall part by hermetically sealing theconductor to a surrounding insulator and providing a supporting member,joined to the wall part to abut a shoulder on the insulator and resistthe tendency of the insulator to move under the influence of the largedifferential pressures acting on it.

While not limited thereto, the invention has been found especiallyapplicable in connection with high pressure switches of the liquidcontact type and in the following description will be exempliiied byreference to such a switch..

For convenience in illustrating one embodiment of the invention it willbe described as applied to a switch of the type disclosed in mycopending application, S. N. 331,797, iiled April 26, i940, and assignedto the assignee of the present application.

The novel features of my invention will be described with greaterparticularity in connection with the accompanying drawing and set forthin the accompanying claims.

In the drawing, Fig. l is a longitudinal section of a circuit breakerutilizing the insulator supporting and sealing means of this invention;Fig.

2 is an enlarged sectional View of my improved insulator supporting andsealing means; and Fig. 3 is a perspective view of a part of the circuitbreaker illustrated in Fig. 1.

Referring now to Fig. 1, I have illustrated my invention as applied to acircuit breaker I0 employing a liquid contact material, such as mercury,which circuit breaker comprises a pressureconfining casing Il,illustrated as a metallic cylinder so constructed as towithstand'relatively high pressures therein. One end of casing II isclosed by a metallic closure member I2 preferably welded thereto andassociated with a suitable threaded terminal I3 through whichconnections to an external circuit may readily be made. A suitablepassage I4 is provided in closure member I2 and is sealed ofi at I5 asby welding when the circuit breaker has been completely constructed andnlled with an appropriate gas (e. g., hydrogen) under pressure. Theother end of the pressure confining casing II is provided with aterminal I6 which is supported relative to casing II by means oi thesupporting structure of this invention hereinafter to be described.

The terminal I supports at its inner extremity, that is, within thecasing l I, a complex electrode 2| having two Contact portions 22 and 22and an intermediate portion 22 which connects the two contact portions(see Fig. 3). During the normal use of the switch the contacts 22 and 22engage a quantity of mercury within the casing and in contact with thecasing walls. For satisfactory operation the casing should be lled withmercury to the level indicated by the dotted line 20. With thisarrangement a complete circuit is provided through the switch betweenthe terminals I3 and I6.

In order to facilitate the circuit-interrupting function of the switch,there is further provided within the switch casing I I a cup-shapedmember Il of insulating material which is held in abutment with thesurface of the electrode contact part 22 kby means of a compressionspring I8. The 'cup Il, which is preferably of ceramic material, isprovided with a shallow end, remote from the supporting means I8 andclosed by a barrier or dam I9. In operation, the switch circuit isbroken by tilting the surface so that the dam I9 cuts the surface of themercury in the manner explained in my above-mentioned copendingapplication. In order additionally to assist the circuit-interruptingoperation, there is associated with the electrode structure 2i an arcchute 23 which is provided with ends 2li and 25 and a top cover member2S adapted to prevent arc gases from escaping the` confining spaceformed by the chute. Also associated with this arc chute is a deionizingmeans 21 comprising alternate layers of iiat and corrugated screen.Furthermore, pressure-contining casing I l is provided with aninsulating liner 28 to prevent any arcing to the walls of the casing Il.

In order to permit the arc which is formed across barrier I9 during thecircuit-interrupting operation to be forced into the arc chute 23,.

magnetic means in the form of a horse-shoe shaped electromagnet 2Q (Fig.3) is provided. This electromagnet is mounted outside the Walls of theceramic cup il with its poles adjacent to the ybarrier i9. A number ofturns of the part 22 are wound around the central portion of theelectromagnet 2Q so that the current owing to the contact r22" throughthis part just prior to complete circuit interruption is enabled todevelop a magnetic field between the poles of the electromagnet. Asuitable insulating means 3l is provided between the structure of theelectromagnet 29 and the' part 22.

United to the inner extremity of the terminal i6 is a. stud 32 having athreaded portion for connection with the electrode 2l. A lock nut 33 isused to insure a tight connection between 32 and 2l.

As has been previously noted herein, my present invention is primarilyconcerned With the problem of providing an insulating seal arrangementfor the terminal l and its associated parts the name of A. W. Hull andRoy W. Moore, and` is in direct sealing contact with a metal sleeve 313which surrounds the terminal I6. It is the function of this sleeve topermit a slight contraction of the glass of the insulator 35 to occurafter the casting procedure without producing an excessive strain suchas might be developed if the glass were welded directly to the rigidstructure of the terminal I6 itself. In order to make the jointlbetizveen the terminal l and the glass insulator oi' gas-tightcharacter, `there is provided a thimble-like member 3l which' is placedover the head of stud 32 and fused into the glass insulator 35,preferably as a part of the original casting operation. The member 3lmay be welded to the stud 32 to provide a hermetic joint.

Embedded in and sealed to the mass of the glass insulator 35 at itsouter circumference is the inner edge of an annular ring 38 whichextends between the insulator and the wall of the metal casing l I towhich it is sealed, for example, by Welding as indicated at All. Inorder to permit slight expansive movement of the casing to occur withoutthereby rupturing the seal between the part 38 and the' glass insulator35, the 'former is due to thermal strains. The relationship of the.`

parts is such that the weight of the insulator 85 f* bent transverselyinto a concave form. Between one of the transversely bent portions ofthe ring and the adjacent surface of the insulator there is provided anidler ring 39 which is in direct sealing engagement with the glass andwhich prevents the glass from sealing to the ring 33 in the regionsubtended by the idler ring.

In order to relieve the strain on the joint between the annular ring 38and the insulator 35 caused by the diiierence in pressure which emstsbetween the outside and inside of the casing li the glass insulator isprovided in accordance with my present invention with a shoulder iiiwhich cooperates with a correspondingly formed surface on the cap partBil of the casing. A lead gasket lli interposed between the shoulder 39and the aforesaid surface of the cap 36 serves to distribute the stressequally over the conical surface of the insulating member 35. Theinternal surface of the cap 3@ also serves as a supporting abutment forthe contour i2 of the member 353. The hermetical closure of thestructure is coin= pleted by means of the Weld i3 between the thin outeredge of the ring li? and the attenuated edge of the cylindricalcontainer l. This weld may. because of its location relative toinsulator 35, be made without danger of cracking the insulator and yofthe elements mounted on it are eectively supported by the cap 3Bindependently of the seal between the part 38 and the insulator therebyrelieving the seal of any strain due to vthis cause.

As a result of the construction described in the foregoing, the sealingarrangement realized is of a character well adapted to withstanddifferential pressures amounting to many atmospheres while providing atthe same time a completely lier= metical seal which does not depend upongasketing to be gas tight. For example, a mercury switch arrangementsuch as that illustrated may employ an internal filling of a gas such ashydrogen at a pressure of as high as pounds per square inch or morewithout danger of iracturingA the seal or developing gas leakage.

In the construction of seals of the character described it is desiredthat the sleeve 3Q, the thimble-like member 3l, the annular ring and theidler ring 3Q be made of a metal having a co= efficient of thermalexpansion substantially the same as that of the insulator material.Numerous sealing combinations which meet reduirea ment are now availableinasmuch as glasses have been developed which are adapted to seal satisufactorily with iron or with alloys of iron with nickel or nickel-cobalt.A

While I have described a particular embodi ment of my invention, itwill. be obvious to these skilled in the art that various changes andmcdl= nca-tions may be made without actually departing from theinvention. I, therefore, desire by the appended claims to cover all suchchanges and modications as fall within the true spirit and scope of theforegoing disclosure.

What I claim as new and desire to by Letters Patent of the United Statesis:

l: A terminal structure for encased electrical apparatus of the typeemplodrig pressures difiering substantially from atmospheric comprisning an insulator having a shoulder portion, a metal ring having one edgeembedded in said insulator and connected to a part of the apparatuscasing to provide a seal for said terminal structure, and another partof the casing engag apparatus subjected to relatively high pressurescomprising an insulator, a shoulder portion on said insulator, a metalring having its inner edge embedded in said insulator adjacent saidshoulder and connected to a portion of the apparatus casing to form aseal, and a further portion of said casing engaging both said shoulderand said metal ring to form a support therefor.

3. A terminal structure for encased electrical apparatus subjected torelatively large pressures, comprising a lead-in conductor for saidapparatus, an insulator surrounding said conductor and sealed thereto, ashoulder on said insulator, a metal expansion ring embedded in saidinsulator adjacent said shoulder and sealed to a part of the casing forsaid apparatus, a portion of said metal ring conforming to one contourof saidshoulder, an idler `ring disposed between the shoulder and themetal ring, and another part of said casing abutting another contour ofsaid shoulder and a second portion of the metal ring to provide asupport for both said metal ring and said shoulder.

4. A terminal structure for encased electrical apparatus of the typeemploying pressures diftering substantially from atmospheric comprisingan insulator having a shoulder portion, a metal ring having one edgeembedded in said insulator and connected to a part of the casing toprovide a seal for said terminal structure, and another part of thecasing engaging said shoulder portion and adapted to absorb mechanicalstresses attributable to said pressure differential, and a deformablegasket interposed between said shoulder and said member to equalize thestresses on said shoulder.

5. An arrangement vfor insulatingly sealing an electrical conductorthrough a wall part having differential pressures on opposite sides ofthe Wall part, said arrangement comprising an insulator surrounding andhermetically joined to the said conductor, a metal ring having its inneredge sealed into the outer portion of .the in-l sulator and disposed onthe side of said wall part exposed to the greater of said differentialpressures, a shoulder provided on said insulator adjacent to the regionof its union with said metal ring, and a surface on said wall partabutting said shoulder and an unembedded portion of said ring forresisting the tendency of said insulator and ring to move or becomedeformed under the influence of said diierential pressures.

6. A glass-to-metal seal for joining an insulator to a casingcomprising, a shoulder on said insulator, a metal expansion ringpartially embedded in said insulator adjacent said shoulder and sealedto said casing, a portion of 'said metal ring conforming to one contourof said shoulder, an idler ring'disposed between the shoulder and themetal ring, and a member abutting another contour of said shoulder and asecond portion of the metal ring and joined to said casing to provide asupport 'for both said metal ring and said shoulder.

'7. A glass-to-metal seal for joining an insulator to a wall comprising,a shoulder on said insulator, a metal expansion ring having its inneredge embedded in said insulator adjacent said shoulder and its outeredge sealed to said Wall, a portion of said metal ring conforming to onecontour of said shoulder, and a member abutting another contour of saidshoulder and a second portion of the metal ring and joined to said wallto provide a support for both said metal ring and said shoulder.

8. A glass-to-metal seal for joining an insu lator to a casing`comprising, a shoulder on said insulator, ametal expansion ringpartially embedded in said insulator adjacent said shoulder and joinedto said casing to form a sealing connection between the casing and theinsulator, a portion of said metal ring conforming to one contour ofsaid shoulder, an idler ring disposed between the shoulder and the metalring, a member abutting another contour of said shoulder and a secondportion of the metal ring and joined to said casing toprovied a supportfor d both said metal ring and said shoulder, and a gasket locatedbetween said shoulder and said member to equalize the stress on saidshoulder. CHAUNCEY G. SUITS.

